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The Subsurface Structure of Oblique Impact Craters
The subsurface structure of oblique impact craters Dissertation vorgelegt von Dipl.-Geol. Michael H. Poelchau vom Fachbereich Geowissenschaften der Freien Universität Berlin zur Erlangung des akademischen Grades doctor rerum naturalium (Dr. rer. nat.) Berlin, 2010 The subsurface structure of oblique impact craters Dissertation vorgelegt von Dipl.-Geol. Michael H. Poelchau vom Fachbereich Geowissenschaften der Freien Universität Berlin zur Erlangung des akademischen Grades doctor rerum naturalium (Dr. rer. nat.) Berlin, 2010 Gutachter: 1. PD Dr. Thomas Kenkmann 2. Prof. Wolf-Uwe Reimold Tag der Disputation: 23.02.2010 Statement regarding the contributions of the author and others to this thesis This thesis is comprised of three published, peer-reviewed articles and one submitted manuscript, which each form separate chapters within this thesis. The chapters “Introduction” and “General Conclusions” were written especially for this thesis. The PhD candidate is the first author of two of these articles, and the second author of the third article. The PhD candidate is also the first author of a manuscript currently submitted to Earth and Planetary Science Letters. Therefore, these four chapters have their own introduction, methodology, discussion, conclusions and references. The articles and manuscripts used in this thesis are the following: Poelchau, M. H., and T. Kenkmann, 2008. Asymmetric signatures in simple craters as an indicator for an oblique impact direction, Meteoritcal and Planetary Science, 43, 2059-2072. Poelchau M. H., Kenkmann T. and Kring D. A., 2009. Rim uplift and crater shape in Meteor Crater: the effects of target heterogeneities and trajectory obliquity. Journal of Geophysical Research, 114, E01006, doi:10.1029/2008JE003235. Kenkmann, T. -
The Cratered Earth
Lunar and Planetary Science XXXIII (2002) sess33.pdf Tuesday, March 12, 2002 POSTER SESSION I 7:00–9:30 p.m. Gymnasium The Cratered Earth Ormö J. Rossi A. P. Komatsu G. Marchetti M. De Santis A. The Discovery of a Probable Well-preserved Impact Crater Field in Central Italy [#1075] We propose the first impact craters found in Italy. They form a crater field with about 17 craters in the range 2- 20 m, and a main crater 140x115 m. It represents a rare example of well-preserved explosion craters formed in unconsolidated targets. Rossi A. P. Seven Possible New Impact Structures in Western Africa Detected on ASTER Imagery [#1309] Seven possible impact structures have been found in W Africa on ASTER images. Their diameters vary from few hundreds of meters up to few kilometers. They are located in Mauritania, Mali and Niger, on a sedimentary or metamorphic bedrock. Miura Y. Hirota A. Gorton M. Kedves M. Impact-related Events on Active Tectonic Regions Defined by Its Age, Shocked Minerals and Compositions [#1231] New type of impact-related event is defined at active tectonic region by using semi-circular structure, bulk XRF compositions with mixed data, shocked quartz grains with the PDFs texture, and Fe-Ni content. Example is discussed in Takamatsu MKT crater in Japan. Krochuk R. V. Sharpton V. L. Overview of Terny Astrobleme (Ukrainian Shield) Studies [#1832] A brief summary of Terny astrobleme observations, including history, petrographic and mineralogical evidences of impact, structure of the crater at current erosion level. Pesonen L. J. Reimold W. U. -
The Geological Record of Meteorite Impacts
THE GEOLOGICAL RECORD OF METEORITE IMPACTS Gordon R. Osinski Canadian Space Agency, 6767 Route de l'Aeroport, St-Hubert, QC J3Y 8Y9 Canada, Email: [email protected] ABSTRACT 2. FORMATION OF METEORITE IMPACT STRUCTURES Meteorite impact structures are found on all planetary bodies in the Solar System with a solid The formation of hypervelocity impact craters has surface. On the Moon, Mercury, and much of Mars, been divided, somewhat arbitrarily, into three main impact craters are the dominant landform. On Earth, stages [3] (Fig. 2): (1) contact and compression, (2) 174 impact sites have been recognized, with several excavation, and (3) modification. A further stage of more new craters being discovered each year. The “hydrothermal and chemical alteration” is also terrestrial impact cratering record is critical for our considered as a separate, final stage in the cratering understanding of impacts as it currently provides the process (e.g., [4]), and is also described below. only ground-truth data on which to base interpretations of the cratering record of other planets and moons. In this contribution, I summarize the processes and products of impact cratering and provide and an up-to-date assessment of the geological record of meteorite impacts. 1. INTRODUCTION It is now widely recognized that impact cratering is a ubiquitous geological process that affects all planetary objects with a solid surface (e.g., [1]). One only has to look up on a clear night to see that impact structures are the dominant landform on the Moon. The same can be said of all the rocky and icy bodies in the solar system that have retained portions of their earliest crust. -
Australian Aboriginal Geomythology: Eyewitness Accounts of Cosmic Impacts?
Preprint: Submitted to Archaeoastronomy – The Journal of Astronomy in Culture Australian Aboriginal Geomythology: Eyewitness Accounts of Cosmic Impacts? Duane W. Hamacher1 and Ray P. Norris2 Abstract Descriptions of cosmic impacts and meteorite falls are found throughout Australian Aboriginal oral traditions. In some cases, these texts describe the impact event in detail, suggesting that the events were witnessed, sometimes citing the location. We explore whether cosmic impacts and meteorite falls may have been witnessed by Aboriginal Australians and incorporated into their oral traditions. We discuss the complications and bias in recording and analysing oral texts but suggest that these texts may be used both to locate new impact structures or meteorites and model observed impact events. We find that, while detailed Aboriginal descriptions of cosmic impacts and meteorite falls are abundant in the literature, there is currently no physical evidence connecting any of these accounts to impact events currently known to Western science. Notice to Aboriginal Readers This paper gives the names of, or references to, Aboriginal people that have passed away throughout, and to information that may be considered sacred to some groups. It also contains information published in Nomads of the Australian Desert by Charles P. Mountford (1976). This book was banned from sale in the Northern Territory in 1976 as it contained sacred/secret knowledge of the Pitjantjatjara (see Brown 2004:33-35; Neate 1982). No information about the Pitjantjatjara from Mountford’s book is presented in this paper. 1 Department of Indigenous Studies, Macquarie University, NSW, 2109, Australia [email protected] | Office: (+61) 2 9850 8671 Duane Hamacher is a PhD candidate in the Department of Indigenous Studies at Macquarie University in Sydney, Australia. -
The Central Uplift of Spider Crater, Western Australia
Large Meteorite Impacts and Planetary Evolution V (2013) 3025.pdf THE CENTRAL UPLIFT OF SPIDER CRATER, WESTERN AUSTRALIA. T. Kenkmann1 and M. H. Poelchau1, 1Institute of Earth and Environmental Sciences, Albert-Ludwigs Universität Freiburg, Albertstraße 23-B, 79104 Freiburg, Germany, [email protected]. Introduction: The Spider impact crater, Australia (13 Macrostructures and kinematic model: The central x 11 km Ø, N16°44’27’’, E126°05’21’’) named after uplift consists of two imbricate thrust stacks that sur- the peculiar appearance of its central uplift, is situated round the core of the structure, indicating N-S shorten- on the Kimberley-Plateau in Western Australia. J. E. ing with a preferred material transport top to southerly Harms was the first who recognized the structure direction (Fig. 1). Dipping of beds within the imbricate around 1960, but twenty years later a cryptovolcanic stacks ranges between 20-80° (40° mean dip) and origin was still favored [1]. Shoemaker and Shoemaker shows no systematic change from N to S. The traces of [2, 3] mapped the site in 1984-85. McHone [4, 5] and each thrust are bent and their strike gradually shifts Abels [6, 7] investigated the structure by means of from N to S. To explain the change in orientation of remote sensing analyses. While most authors favored the thrust slices from up range to downrange a very an oblique impact from N to NW to explain the nor- simple approach of vector summation in a horizontal therly dipping thrust stacks [2, 3], Abels [6, 7] argued plane might be helpful: An idealized flow field during that pre-impact topography and the (very) gently dip- crater collapse at a vertical incidence is represented by ping limbs of the broad Mt. -
Appendix: Planetary Facts, Data and Tools
Appendix: Planetary Facts, Data and Tools Planetary Constants See Tables A1 and A2. © Springer International Publishing AG 2018 395 A.P. Rossi, S. van Gasselt (eds.), Planetary Geology, Springer Praxis Books, DOI 10.1007/978-3-319-65179-8 396 Appendix: Planetary Facts, Data and Tools Table A1 Bulk parameters for planets, dwarf planets and selected satellites Polar Equatorial Inverse Magnetic Atmospheric Mass radius radius flattening Density Gravity field pressure 24 3 2 Discovery Moons m [10 kg] rp [km] re [km] 1/f [–] [kg/m ] g [m/s ] B [T] p [bar] Planets Mercury prehistoric 0 0:330 2439:7 2439:7 – 5427 3:710 3.0107 1014 Venus prehistoric 0 4:868 6051:8 6051:8 – 5243 8:870 – 92 Earth prehistoric 1 5:972 6356:8 6378:1 298:253 5514 9:810 2.4105 1.014 Mars prehistoric 2 0:642 3376:2 3396:2 169:894 3933 3:710 – 0.006 Jupiter prehistoric 67 1898:190 66854:0 71492:0 15:41 1326 24:790 4.3104 > 1000 Saturn prehistoric 62 568:340 54364:0 60268:0 10:21 687 10:440 2.2105 > 1000 Uranus 1781 27 86:813 24973:0 25559:0 43:62 1271 8:870 2.3105 > 1000 Neptune 1846 14 102:413 24341:0 24764:0 58:54 1638 11:150 1.4105 > 1000 Dwarf m [1021 kg] planets (134340) 1930 5 13:030 1187:0 1187:0 – 1860 0:620 – 1109 Pluto (1) Ceres 1801 0 0:939 473:0 473:0 – 2161 0:280 – – (136199) 2005 1 16:600 1163:0 1163:0 – 2520 0:820 – – Eris (136472) 2005 1 < 4:400 715:0 715:0 20:00 1400 0:500 – 4–12109 Makemake 739:0 739:0 3200 (136108) 2004 2 4:010 620:0 620:0 – (min) 0:630 – – Haumea 2600 Appendix: Planetary Facts, Data and Tools 397 Satellites m [1021 kg] Earth’s moon -
A New Type of Highly-Vaporized Microtektite from the Transantarctic Mountains
Available online at www.sciencedirect.com ScienceDirect Geochimica et Cosmochimica Acta 228 (2018) 81–94 www.elsevier.com/locate/gca A new type of highly-vaporized microtektite from the Transantarctic Mountains M. Van Ginneken a,b,1,2,⇑, M.J. Genge a, R.P. Harvey c a IARC, Department of Earth Science and Engineering, Imperial College London, Exhibition Road, London SW7 2AZ, UK b Department of Earth Science, The Natural History Museum, London SW7 2BT, UK c Department of Geological Sciences, 112 A. W. Smith Building, Case Western Reserve University, Cleveland, OH 44106-7216, USA Received 9 June 2017; accepted in revised form 23 February 2018; Available online 6 March 2018 Abstract We report on the discovery of microtektites (microscopic impact glass spherules) in a glacial moraine near Larkman Nunatak in the Transantarctic Mountains, Antarctica. The microtektites were identified based on their physical and chemical properties. Major and trace element compositions of the particles suggest that they may be related to the Australasian strewn field. This would further extend the current strewn field 800 km southward. Depletion in volatiles and enrichment in refrac- tory elements in Larkman Nunatak microtektites fit the volatilization trend defined by Australasian microtektites, suggesting that they may represent a new highly vapor fractionated end-member thereof. This observation is supported by their low vesicularity and absence of mineral inclusions. This discovery has significant implications for the formation of microtektites (i.e. their evolution with respect to the distance from the source crater). Finally, the discovery of potentially old (i.e. 0.8 Ma) microtektites in moraine has implications for the stability of the East Antarctic Ice Sheet in the Larkman Nunatak area over the last 1 Ma and, as a consequence, the high efficiency of such moraines as traps for other extraterrestrial materials (e.g. -
SRTM As-Flown Mission Timeline
SRTM As-Flown Mission Timeline 16 May 2000 Issued by: D. Seal / F. Rogez J N 1. Introduction This document contains technical information relevant to Mission Planning for the Shuttle Radar Topography Mission (SRTM). It includes the as-flown events executed during the mission. This timeline serves to guide post-mission reconstruction and data processing is under control of the Mission Operations System. The SRTM mission launched on February 11, 2000 at 12:44am EST (exact GMT was 17:43:39.961) aboard the space shuttle Endeavor (STS-99) for a mission duration of 11 days, 5 hours, and 38 minutes. The high-level timeline for the SRTM mission was as follows: Mapping began at MET 00/11:47, several hours earlier than expected after a nominal OOCO using plan A Mapping ended at MET 09/18:10, earlier than the required 10/07:30 to complete the repeat cycle, but enough to get 99.96% of the target land imaged at least once Mast stow ended at 09/22:07 on the fifth attempt Nominal de-orbit burn was at 11/04:48 Nominal landing at KSC 11/05:38 (February 22, 2000 at 6:22pm EST) This report, along with other as-flown resources, are available electronically at the Mission Planning document library at “http://samadhi.jpl.nasa.gov/srtm”. 2. Orbit Characteristics During the flight, the shuttle characteristics and orbital perturbations were modelled as follows: Orbiter coefficient of drag (Cd) = 2.0 Orbiter weight = 242200.0 pounds mass at launch, dropping smoothly to 234257 pounds mass at end of mapping Area = 1577 square feet 90-day mean solar flux (f10.7) = 172.0 Geomagnetic planetary index (kp) = 2.38 Drag weighting factor for vernier firings, vent forces, etc. -
Amelia Creek: a Proterozoic Impact Structure in the Davenport Ranges, Northern Territory
Australian Journal of Earth Sciences (2005) 52, (631 – 640) Amelia Creek: a Proterozoic impact structure in the Davenport Ranges, Northern Territory F. A. MACDONALD,1* K. MITCHELL2 AND A. J. STEWART3 1Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138, USA. 281 Fern Street, Gerringong, NSW 2534, Australia. 323 Vasey Crescent, Campbell, ACT 2612, Australia. The Amelia Creek impact structure is located in Australia’s Northern Territory in folded Palaeoproter- ozoic strata of the Davenport Ranges (20851’S, 134853’E). An impact origin is confirmed by presence of unequivocal shatter cones with apices that point upwards, and by planar microstructures in quartz grains from target sandstones of the Hatches Creek Group. Aeromagnetic, advanced spaceborne thermal emission and reflection radiometer (ASTER), and X-band synthetic aperture radar (X-SAR) images show an area of anomalous deformation in which smooth regional trends are disrupted by arcuate features at a 10 km radius to the north and south of the shock-metamorphosed rocks. However, no arcuate forms are apparent to the east and west of these shocked rocks, and instead, large south-southwest-trending faults are present about 6 km away on both sides. Despite pervasive shatter coning, typical of the central region of complex impact structures, no structural uplift is apparent, but instead the shocked rocks lie at the southern toe of a north-northeast-trending syncline. These shatter cones overprint and post-date the Palaeoproterozoic regional deformation, and thus, the impact structure has not been refolded and its abnormal form is likely due to pre-existing structure in the target rocks and/or an oblique impact. -
Ramgarh, Rajasthan, India: a 10 Km Diameter Complex Impact Structure
Meteoritics & Planetary Science 55, Nr 4, 936–961 (2020) doi: 10.1111/maps.13454 Ramgarh, Rajasthan, India: A 10 km diameter complex impact structure Thomas KENKMANN 1,*, Gerwin WULF1, and Amar AGARWAL1,2 1Institute of Earth and Environmental Sciences—Geology, Albert-Ludwigs-Universitat€ Freiburg, Albertstrasse 23-B, 79104 Freiburg im Breisgau, Germany 2Department of Earth Sciences, Indian Institute of Technology-Kanpur, Kanpur-208016, India Corresponding author: E-mail: [email protected] (Received 14 June 2019; revision accepted 26 January 2020) Abstract–The Ramgarh structure is a morphological landmark in southeastern Rajasthan, India. Its 200 m high and 3.5–4 km wide annular collar has provoked many hypotheses regarding its origin, including impact. Here, we document planar deformation features, planar fractures, and feather features in quartz grains of the central part of the Ramgarh structure, which confirm its impact origin. The annular collar does not mark the crater rim but represents the outer part of a central uplift of an approximately 10 km diameter complex impact structure. The apparent crater rim is exposed as a low-angle normal fault and can be traced as lineaments in remote sensing imagery. The central uplift shows a stratigraphic uplift of ~1000 m and is rectangular in shape. It is dissected by numerous faults that are co-genetic with the formation of the central uplift. The central uplift has a bilateral symmetry along an SW-NE axis, where a large strike-slip fault documents a strong horizontal shear component. This direction corresponds to the assumed impact trajectory from the SW toward the NE. -
The Geological Record of Meteorite Impacts
THE GEOLOGICAL RECORD OF METEORITE IMPACTS Gordon R. Osinski Canadian Space Agency, 6767 Route de l'Aeroport, St-Hubert, QC J3Y 8Y9 Canada, Email: [email protected] ABSTRACT 2. FORMATION OF METEORITE IMPACT STRUCTURES Meteorite impact structures are found on all planetary bodies in the Solar System with a solid The formation of hypervelocity impact craters has surface. On the Moon, Mercury, and much of Mars, been divided, somewhat arbitrarily, into three main impact craters are the dominant landform. On Earth, stages [3] (Fig. 2): (1) contact and compression, (2) 174 impact sites have been recognized, with several excavation, and (3) modification. A further stage of more new craters being discovered each year. The “hydrothermal and chemical alteration” is also terrestrial impact cratering record is critical for our considered as a separate, final stage in the cratering understanding of impacts as it currently provides the process (e.g., [4]), and is also described below. only ground-truth data on which to base interpretations of the cratering record of other planets and moons. In this contribution, I summarize the processes and products of impact cratering and provide and an up-to-date assessment of the geological record of meteorite impacts. 1. INTRODUCTION It is now widely recognized that impact cratering is a ubiquitous geological process that affects all planetary objects with a solid surface (e.g., [1]). One only has to look up on a clear night to see that impact structures are the dominant landform on the Moon. The same can be said of all the rocky and icy bodies in the solar system that have retained portions of their earliest crust. -
The Search for Shocked Zircon at Spider Impact Structure, Western Australia
49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083) 1890.pdf The Search for Shocked Zircon at Spider Impact Structure, Western Australia. Morgan. A. Cox1, Aaron. J. Cavosie1,, Katarina Miljković1, Phil A. Bland1, and Thomas Kenkmann2 1School of Earth and Planetary Sciences, Curtin University, Perth, Australia. 2Institute of Earth and Environmental Sciences—Geology, Albert-Ludwigs-Universität (ALU) Freiburg, Albertstraße 23B, Freiburg 79104, Germany. Email: [email protected] Introduction: Impact cratering is an important and shock microstructures above 20 GPa [5]. More recently, widespread geological process throughout the solar sys- the phosphate mineral xenotime (YPO4) has been found tem, and shocked minerals provide diagnostic criteria to form shock microstructures at pressures below 20 used in confirming an impact event [1]. GPa [11], and thus has great potential for recording im- Spider impact structure is located ~430 km NE of pact evidence. Broome, Western Australia, and is a confirmed meteor- The central uplift at Spider crater exposes the War- ite impact structure through identification of shatter ton sandstone (1704±7 to 1786±14 Ma) and Pentecost cones and shocked quartz [2,3], both diagnostic criteria sandstone (1704±14 to 1774±9 Ma) [2,12], both of used to confirm impact events. Shocked zircon, how- which underwent diagenesis pre-impact [12,13]. This ever, has yet to be reported at the Spider structure. Here, resulted in formation of ubiquitous diagenetic xenotime we report preliminary results of our search for shocked overgrowths around detrital zircon grains, both of which zircon at the Spider impact structure. would have been shocked during the impact.